Major construction is about to start along the Interstate 5 corridor that runs along a portion of Joint Base Lewis-McChord.

This work is the second stage of four to improve traffic flow on I-5 through JBLM. The $495 million effort is scheduled to be complete in 2025. This second stage, which will be done in 2021, will increase freeway capacity by adding a lane in both directions from just north of Steilacoom-DuPont Road (exit 119 by the DuPont Gate on JBLM) to Thorne Lane in Lakewood (exit 123 near the Logistics Center Gate on JBLM).

The first stage was adding an auxiliary lane between Mounts Road and Center Drive.

Auxiliary lanes will also be added between Berkeley Street (exit 123 near the Madigan Gate) and Gravelly Lake Drive (exit 124 located between the McChord Field Housing and the Logistics Center gates). New interchanges at Thorne Lane and Berkeley Street will be constructed over the existing high-speed rail line, which eliminates potential conflicts with trains.

The new overpasses will be built adjacent to the existing structures, which minimizes closures during construction. But there will still be some growing pains.

The growing pains began Tuesday, Sept. 4, through Thursday, Sept. 6, when preparatory work began on Union Avenue. During the work, Union Avenue, between Spruce Street SW and Thorne Lane, will close each night from 8 p.m. to 4:30 a.m. Drivers will follow signed detour routes.

Other impacts throughout the duration of the project include:

Night lane closures

Narrowed lanes on I-5

Some minor night impacts to city streets

Partial night ramp closures and some total night closures of mainline I-5 during bridge demolition and girder placement

Weekend closures and one extended closure of Berkeley ramps to construct new overpass and Berkeley on-ramp to northbound I-5

One weekend closure of the Madigan Gate

Extended closure of Union Avenue at Thorne to raise profile of Union Avenue to meet height of new overpass.